New alpine lake a dam fine prospect
25 Oct 2007
A newly formed lake in the South Island is holding on to potentially become the newest attraction at the Mt Aspiring National Park.
The 2.5km long, 500m wide and 100m deep lake in the Young Valley was created after a large landslip blocked the river in August. If the blockage continues to hold, the lake would be the newest addition to park's already plentiful attractions.
GNS geologist and engineer Stuart Read said there was a chance the lake's dam could hold.
"When you look at the history of these sorts of dams, they have a tendency to fail. But there are exceptions. A lot depends on the type of land slide that forms," Mr Read said.
Water has been flowing over the top but there were concerns that recent heavy rain could burst through the dam, causing millions of cubic metres of water to rush down the valley. But so far the dam had not weakened and if anything, it may've been strengthened by the multiple earthquakes that have since rocked the South Island.
Mr Read said New Zealand's best known example of these types of lakes was Lake Waikaremoana, in the Urewera National Park.
He said the survival of the dam was dependent on the type of rock in the landslide and whether the landslide blocks the waterway with large masses of rock or sediment.
Gavin Palmer from the Otago Regional Council recently visited the lake to investigate the condition of the dam.
He said water was seeping through the dam but that had now dried up. Dr Palmer said water was still flowing over the top but he confirmed the dam could hold and the council would continue to monitor the lake.
The lake has not yet been given a name and Land Information New Zealand spokeswoman Julia Hodge said the geographic board would need scientific evidence to prove that the lake was a permanent feature.
Further information:
Dr Gavin Palmer
Director Environmental Engineering and Natural Hazards
Otago Regional Council
Mobile: +64 27 493 3960
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